Location-Aware applications are built on the knowledge of a mobile device's current geographic position as well as the knowledge of geographic positions of other users, places, or things. Mobile devices often recalculate their position very frequently, up to multiple times in a single second in some systems. Using positioning systems such as Global Positioning Systems (GPS) to frequently recalculate the position of the mobile device costs energy. Additionally, transferring that updated location data from the device to a server or another device through wireless communications also costs energy. Therefore, even though it is desirable to frequently update the system (including mobiles devices and servers) with the knowledge of the position of the device, there is a significant resource cost involved in both the position calculation and wireless transfer of data.
To save device resources, including power, during repeated transmissions of position data, “unreliable” or “connectionless” protocols such as User Datagram Protocol (UDP) can be used. UDP does not verify the receipt of data packets or the order in which they are received, whereas “reliable” or connection-oriented protocols, such as Transmission Control Protocol (TCP), do. However, UDP also avoids the extra transmission overhead that TCP requires in order to acknowledge the receipt of packets and request the re-submission of packets that were lost or corrupted. Therefore, UDP costs less energy per location data packet transferred than TCP and, therefore, is preferred when repeatedly transferring location data from (and to) a mobile device. Additionally, the entity (e.g. server or mobile device) receiving the data is not under as much of a strain because it does not have to acknowledge the receipt of each packet.
However, because UDP is unreliable, the receipt of location data by the receiving party is not guaranteed. In wireless systems that are highly likely to have lost or corrupted data packets, as well as a mobile device such as a mobile phone that may prevent the transfer or reception of data at certain times (i.e. during an active phone call, lack of cell phone signal), a large amount of data may be lost if the ordinary UDP protocol is used. Also, significant device battery life is unnecessarily wasted when transmitting via UDP if the other entity is not receiving the information.